Many prescription medications have "off-label" uses, and antidepressants are no exception. A 2017 survey conducted by the Centers for Disease Control and Prevention found that approximately 1 in 9 Americans had taken at least one antidepressant medication in the past month. Depression is one of the most prevalent mental illnesses, but not every antidepressant prescription is written to treat the condition. Many doctors prescribe antidepressants for other physical and mental health reasons, such as the following.

1. Migraine headaches

Many different antidepressants have been shown to be helpful with headaches, physician Dr. Edward J. Bilotti tells SheKnows. "The tricyclic antidepressant nortriptyline is the one most commonly prescribed for migraine," he says.

2. Neuropathic pain

Neuropathic pain, which is caused by nerve irritation or nerve pathology, is often treated with serotonin-norepinephrine reuptake inhibitors and tricyclic antidepressants, Bilotti explains. "The exact mechanism by which they help with pain is not fully known but it is believed to be related to the fact that norepinephrine inhibits pain in the spinal cord," he adds, noting that this is why these classes of antidepressants can also help with fibromyalgia pain.

"The mechanism of action of these drugs appears to be different for pain than for depression, but neither are fully known," Bilotti says.

3. Sleep disorders

Dr. Prakash Masand, psychiatrist and founder of the Centers of Psychiatric Excellence, tells SheKnows that some antidepressants are prescribed for sleep abnormalities, especially insomnia.

"Some patients report better relief compared to traditional sleep aids," Masand says. "The other benefit to antidepressants is that sleep aids are powerful narcotics and can become addictive."

4. Quitting smoking

Masand says that one antidepressant in particular is used to help people quit smoking. "Zyban, a common smoking cessation medication, is actually the drug bupropion," he explains. "This is an extended-release antidepressant that targets brain chemicals associated with cravings."

5. Eating disorders

"It is believed that patients with bulimia may suffer from a chemical imbalance of serotonin, a neurotransmitter that antidepressants specifically target," Masand says.

Bilotti adds that the mechanism is not well understood, but it's believed to be partly due to the overlap between obsessive-compulsive symptoms, anxiety and depression that occur with eating disorders.

6. Menopausal symptoms

"Menopausal symptoms like hot flashes and dysphoric mood (sad, irritable) can be helped with [a serotonin-norepinephrine reuptake inhibitor]," Bilotti explains. It's believed that the effects of norepinephrine on the central and autonomic nervous system are what help ease these menopausal symptoms, he adds.

7. Cardiovascular diseases

Depression and/or anxiety related to cardiovascular diseases such as heart attack or stroke are common, Bilotti says, and in these cases, it's common to prescribe a selective serotonin reuptake inhibitor.

8. Chronic pain

Regardless of its root cause, chronic pain patients are sometimes treated with antidepressants. "Physical pain and depression go hand in hand," Bilotti explains. "People in pain can become depressed, and depressed people tend to experience pain worse or more [severely] than if they were not depressed."

9. Panic disorder & PTSD

In addition to treating major depression, selective serotonin reuptake inhibitors are often prescribed to people who have been diagnosed with panic disorder and post-traumatic stress disorder. Masand says that this is because SSRIs target serotonin in the brain — a chemical that is believed to play a role in other mental health conditions such as panic disorder and PTSD.

So, if your doctor talks to you about starting antidepressants, be sure to ask plenty of questions (as with any new medication) and know that they're prescribed for a variety of conditions — not all of which are directly related to mental health.